What is my healthiest weight?

Results:

According to a  research article published in the New England Journal of Medicine, the  mortality rate for white, disease free non-smokers of your sex reaches a minimum value at a BMI of kg/m2 .   The relative mortality rate increased 20% or more above the minimum for BMI values lower than kg/m2  or higher than kg/m2.   Most adults should maintain their BMI in the range provided. (Experimental results were different from white and blacks, and the study excluded other races.  See details below.)

For convenience, I have translated the BMI range provided above to a weight range for someone of your height.  The weight range for a person of your height and sex is to . If your BMI falls in this range, your weight is appropriate for your height.  Either a higher or lower BMI are associated with increased mortality. (Note: most articles will describe the ideal BMI range as falling between 20 and 25.  I'm giving you the range that describes a 20% increase in mortality based on the article cited below.)

You can evaluate the relative mortality associated with your BMI by examining the plots provided below. You can also read some other details associated with the study.

What if your BMI falls outside the range specified?

Well, BMI is a marker that suggests a level of fitness.  It is not, in and of itself, a complete measure of fitness.

Most fit people have BMI's in the healthy range but some people with appropriate BMI are unfit.  Still, BMI is considered a "marker" for a healthy body composition. Most people with high BMI's have excess fat which is a health hazard.  A small fraction of people with high BMI's are very muscular which is thought to be healthy. (Examples reported in the July 23 issue of the Wall Street Journal include Arnold Schwarzenegger BMI = 33, Sammy Sosa, BMI = 30).  Most people with low BMI's either lack  adequate muscle mass, or have dangerously low fat levels.

Since BMI is just a marker, and not an absolute measure, it is useful to investigate further and determine whether you have inadequate muscle mass, dangerously low or high fat levels.

To determine whether you have adequate muscle mass or excess fat, you should measure your body fat percentage.  It is also useful to monitor your fitness level, but that is a separate issue from weight, so I don't discuss that here. You might also want to investigate your distribution of fat.  To do that, visit my Apple vs. Pear page.

Body fat is more difficult to measure than weight.  Still, you can estimate your body fat percentage yourself.  You can purchase a set of skin fold calipers and use their body fat charts, or you can weigh yourself on a special scale that measures the electrical impedance of your body.  I've done both.  The skin fold calipers are less expensive. The scale is very easy to use and I'm extremely happy with it. HealthTrack and BigFitness both offer convenient and accurate body fat monitors and scales for one or the whole family.   If you don't want to spend any money, you can also get an estimate using a tape measure. (I'm somewhat suspicious of the tape measure methods, but heck, those are the equations I found.)

Percent Body Fat

Afterwards, click somewhere outside the box.  The boxes in the remaining discussion will fill with values tailored to you. Otherwise, the discussion will use the default value of 30% (which is roughly the body fat percentage for a typical American woman.)

First, compare your body fat to the ideal range for an adult of your sex; this is:  to % . The lower value is usually achieved by young athletic individuals. The higher value is more representative of healthy adults who don't happen to be professional athletes or aerobics instructors. (In fact, some professional athletes fall near the top of the range.)  If your body fat falls within this range you can probably disregard a high BMI. Your fat level is not too high; you are muscular.  Good for you!

What if your BMI is low or ideal and your body fat percentage is high?  That could be bad; continue reading.  You probably have too little lean muscle.  It is best to correct this because inadequate muscle mass sets you up for a number of health problems.  Thin women tend to get osteoporosis and break their bones.  Injuries due to osteoporosis is the primary reason women end up in nursing homes; so do try to avoid that.  For more information, read "Strong Women Stay Young" or "Strong Women Stay Slim," by Miriam Nelson, Ph. D.)

Suppose you are unhappy with your body fat percentage?  Then you must determine whether your problem is too much fat, too little lean muscle or both.  Most Americans carry an unhealthy amount of fat; strangely, many also carry too little lean muscle.  And guess what? If your lean muscle is too low, it is more difficult to lose weight because supposedly, at rest a pound of muscle burns more calories than a pound of fat.  So, you may want to increase muscle in order to lose fat!
 

Lean Body Mass

I constantly read exercise books telling me that low lean body mass has adverse health consequences.  But the articles never include numbers to describe adequate levels of lean muscle mass! So, I calculated a few numbers based on the range of healthy BMI and acceptable body fat percentages.  I suggest you compare your lean mass to the two minimal values I calculated for your height and sex.

A lean body mass of  corresponds to a person with the lowest healthy BMI and the lowest healthy body fat percentage.   It seems to me this is a "minimal healthy" value.

If your muscle is lower than this "minimal healthy value", I'd say you are an "absolute wimp."  Need help to open jars?  Think carrying groceries is difficult?  Can't pick up a toddler and carry them for 5 minutes? I rest my case.

If your lean muscle mass falls below the lower value, you should strongly consider strength training!  Low muscle mass is associated with osteoporosis, which is a frequent cause of severe disability particularly in women over 50. (If osteoporosis gallops in your family, like it does in mine, it can strike earlier.)  One caution, if you think you may have low bone density, you should consult your physician before starting strength training.  They will probably support the idea of strength training.  However, they will probably advise you to start out slowly using fairly light weights.   (I think everyone should start slowly anyway for reasons unrelated to osteoporosis.) If you have severe symptoms of osteoporosis or have already experienced fractures, your doctor will probably insist you be supervised during initial strength training sessions.

It seems to me that  is a more appropriate minimal value for lean body mass.  This corresponds to a person with the ideal healthy BMI and a body fat percentage in the middle of the ideal range for your sex.  In my opinion, if your muscle is lower than this, you should do strength training to increase muscle. Heck, you probably need strength training to maintain what you have.

My lean body mass falls below this level, I am strength training to build muscle.  (Yes, I am a borderline wimp.)

If your lean body mass is greater than both values provided above, strength training is a matter of personal preference.

What's my personal preference? I'm writing this in late June 2002.  My lean body mass currently falls above the lower "minimal" value and below my recommend value for my height and weight.  I'm a 43 year old, 5'4" woman and I weigh 130 lbs and have 97 lbs of lean mass.  The formula I use to determine the "appropriate minimal value" results in 104 lbs of lean body mass.

I don't think I look muscular.  You can decide for yourself from the pictures I've posted.  I'm pretty sure I'd look better with more muscle.  If I ever make it to 104 lbs of lean body mass, I'll decide whether I've gotten too muscular, or whether I still need more muscle!

When setting your goal for lean body mass, consider this: Some diet and nutrition experts believe that increasing muscle mass will significantly increase the rate your body burns calories.

If true, putting on muscle would permit you to eat more, possible a lot more.  One the other hand, at least one study suggests that bulking up as much as a competitive body builder may be bad for your health; (see: Aerobic Fitness & Health ).  So, you may want to avoid bulking up that much.

Honestly, I'm not worried about bulking up to much though. The fact is, it's not easy to get as big as a body builder!  Both male and female body builders work out a tremendous amount. Women have an especially difficult time increasing muscle mass even when they try.

Are you still worried about bulking up too much if you lift weights?  Why? What's the worst that can happen? Let's say you start strength training and you do suddenly find you've bulked up unimaginably.  Can't you just stop strength training?  Remember: "If you don't use it, you'll lose it!" It's true! If you get too muscular for your taste, just stop. I promise the muscles will vanish.

Ok, so when should you start worrying that you are starting to be "too bulky".  Well, you can probably tell by looking in the mirror!

For reference,  is the muscle mass corresponding to the highest BMI and the highest percentage body fat in the ideal range.  If you have that much muscle, you are getting pretty darn muscular for your height. (Hey, if you can get that big, think about entering a a body building competition.  You've got a chance to be competitive!  Well, honestly, I punched in "Arnold" type numbers.  Male body builders have more much muscle than this!)
 

Body Fat Mass

Bearing in mind that percent body fat is the more useful indicator or health than the absolute fat mass, it is still useful to compare your body fat mass to the acceptable ranges of body fat for people of your sex falling in the ideal BMI and % body fat range. The comparison can help you select a realistic fat loss goal.

The range of fat mass I will calculate for you is designed to span the ideal fat percentage levels and the ideal BMI range. Fat levels that might correspond to the range of possible healthy levels of body fat . Falling inside the range does not guarantee an optimum level of fat; falling outside the probably means your fat level falls outside the "ideal" range. However, some very muscular people may be able to carry even more fat than indicated.

This fat mass value  corresponds to a person with the lowest BMI and lowest body fat percentage in the ideal range. This person is both slender and skinny!  A fat mass of  corresponds to a person with the highest healthy BMI and the highest healthy body fat in the ideal range; in other words a muscular person with the highest body fat level in the ideal range.

If your body fat exceeds the higher of these two values, diet and exercise to reduce body fat would probably improve your health.  Give losing fat serious consideration.

Still, if you are over fat, you should be realistic when setting your goals. If you are currently extremely heavy, even this upper value may be ambitious.  Significant improvements in health can be achieved by reducing your fat mass as little as 10 lbs; why not pick a goal of losing 10 lbs and maintaining muscle mass? You can always reset your goal if you reach it.

Better yet, why not set your goal to maintaining weight and improving fitness?  There is lots of evidence that fitness is more important than weight. If you are sedentary, you can dramatically improve your health if you just start walking 30 minutes a day, three times a week.  Don't worry if you don't lose weight at first. Many people eventually lose weight when they start exercising-- but it takes a while to lose weight when you simply start and exercise program.

In any event, it is best to discuss any diet, exercise or weight loss plan with a physician.  This is particularly true if you are obese, very unfit, or have any symptoms of cardiovascular illness, diabetes or any other illness.

If your body fat level is falls below the lower value, you should probably attempt to gain fat!  Remember, good health requires some body fat.  Studies show that mortality increases for both overweight and underweight individuals. The reason we Americans don't discuss the adverse health consequences associated with being underweight because so few of us are underweight!  If you have low body fat, please discuss your low body fat with your physician and their advise about weight gain or loss.

By the way, thin people should be particularly careful about the risks of depression and infectious disease.  Despite all the diet books that claim over weight is caused by psychological disorders, the fact is that suicide rate is much higher for those with low BMI's.  Death from influenza and other respiratory diseases is also more common at low BMI's. So, if you are thin, please make sure you get flu shots, and watch out for any signs of depression.
 

Note to dieters:

1. people generally lose muscle as well as fat while dieting
2. pound for pound, at rest, muscle typically burns more calories that fat and
3. many studies indicate that it is healthier to be over weight and aerobically fit rather than underweight and unfit.

Detailed discussion of these three points are provided below.

Muscle Loss

Frankly, I haven't been able to figure out whether or not weight training helps prevent loss of muscle during a diet. ( I should do more reading!)  Nelson reports that studies at Tufts University show that weight training does help prevent loss of muscle, while Nieman cites studies that indicate that weight training is of little value.

However, the cited studies seem to differ in the severity of dieting.  The studies cited by Nieman involved near starvation calorie restriction; participants consumed 400-800 calories a day.  Dr. Nelson's book does not specify the calorie consumption of the Tufts participants, but she states they ate "customized food plans designed for slow but steady weight loss."  This is certainly more than 400-800 calories a day!  So, maybe exercising helps retain muscle during a sensible diet, but can't prevent the muscle loss during a severe starvation diet?

The results of these studies may not apply to you, but I'll go ahead and apply them anyway.  Based on these results, it would seem:

• if you followed a 1200 calorie diet without performing strength training exercise and brought your weight down to  , your lean muscle mass would probably drop to .  Your percent body fat would then be %.

• if you followed a 400-800 calorie diet with or without performing strength training, and brought your weight down to  your lean muscle mass would probably drop to . Your percent body fat would then be %. (My advise: don't do this without medical supervision! People have been knows to die during the course of severe calorie restriction.)

Calorie Burning due to Lean Muscle Mass.

The important thing is this: even 21.6 Cal/day is much larger than the more typical 5 Calories/day burned by an "average" pound of body mass which includes bone, fat, internal organs, and muscle.  So your metabolism should get a big boost by increasing muscle!

How much does this extra calorie burning matter?  Well, let's assume I burned an extra 100 Calories/day as a result of gaining 1 to 3 lbs of muscle, and I didn't eat more to compensate. If the Benedict-Harris multiplier for calories used per pound of body mass applies, I would expect to lose between 10 and 15 lbs of fat in the long run.  If the Cunningham equation applies, you'd keep losing weight forever. More likely, you'd lose weight until you began eating to make up for the calorie deficit!

Granted, in either case, it would take me a month to lose the first pound of fat but I wouldn't be dieting.  You know what else?  For me, 10 to 15 lbs represents my entire "weight problem"!  So, I do want to gain a 1-3 pounds of muscle to keep off 10-15 lbs of fat while still eating as I did before I decided to lose weight.

Anyway, it seems to me, to avoid weight gain, it is prudent to:

• avoid severe calorie restriction and
• perform some strength training to build muscle mass.

Fitness vs. Fatness

On Tuesday July 23, 2002, the Wall Street Journal reported interesting data on the effect of fitness on longevity.  Compelling evidence suggests that fitness has a greater impact on longevity than weight.  A  recent study conducted by researchers at the Cooper Institute of Aerobic Fitness indicates that unfit lean men are twice as likely to die as fit men.  Yep, unfit lean mean were even more likely to die than obese fit men. The study which spanned 8 years included, 22,000 men, and is only the most recent of over two dozen studies showing this effect.

The observable fact is this: exercise to improve fitness generally lowers blood pressure, lower cholesterol and improve insulin response. This results in improved longevity.  The exercise sometimes also helps control weight, but the other benefits are more important to your health in the long run.

So, exercise whether or not you decide to lose weight.
 

Final Advice

• If you are overweight, exercise at least 3 times a week to improve your fitness.  If you can, exercise more to lose weight.  Try to follow a balanced diet, and think about portions control.  (In fact, everyone should do this even if they are not overweight.)
• If you are underweight, try to eat more to raise your BMI.  If you are naturally thin, and unable to increase your weight, watch out for depression or flu.
• If you don't have enough muscle, try strength training to improve muscle mass and
• Everyone, create reasonable goals that fit your lifestyle.

Lucia

Details from "Body-Mass Index and Mortality in a Prospective Cohort of U.S. Adults."

1. The study included 1,046,154 participants.  All were over 30 years of age or older.
2. Participants self reported their height and weight. The authors noted people tend to slightly under estimate their weight, and over estimate their height.  This means that the BMI's in this report may be lower than the actual BMI's of the participants.  (But there is no way to correct for this errors due to this known bias.)
3. The study included whites and blacks only. People of other races were excluded.
4. Data for blacks and whites, women and men were analyzed separately.
5. For the purposes of analysis, they divided the male and female participants racial groups, and further four sub-groups.  There were:
• people who never smoked vs. current and past smokers.
•  people with no indication of disease vs. people who had any indication of disease. Indications of disease include: a history of cancer, heart disease, or respiratory disease, current illness of any type, or losing at least 10 lbs in the past year.
6. Detailed mortality data were tabulated for only one of the four sub-groups: people who never smoked who had no symptoms of disease.
7. Plots were provided for other groups. The effect of BMI on mortality for the smokers and people with diseases was different from it's effect on smokers or people with indications of disease.  Generally, the effect of BMI was less important for both smokers and/or people with indications of disease.   Also, being underweight appeared to be more dangerous than overweight to female smokers or females with disease. You'll need to request the paper on interlibrary loan if you wish to see the other plots.

My Discussion and Plot

As you can see, white women had the lowest absolute mortality rates.  Black women, and white men have intermediate mortality rates.  Black men tend to have the highest mortality rates.

Note that there are fewer data points for black men. This is the number of black men in the study was insufficient to permit calculation of their death rates at those BMI levels.

If you read the article itself, you'll see a graph similar to this one.  The authors normalized the data dividing my the "reference" mortality rate.  That is, they divided all the death rates by the death rate near BMI = 24.  This normalized death rate is referred to as the relative mortality.  Plotting the data this way helps us compare the importance of BMI to mortality for white men, white women, black men and black women.

The mortality rate for white men was found to be most strongly affected by increased BMI.  Notice that very heavy men exhibit the greatest elevation in BMI of all groups.  White male mortality also increases at very low BMI's.

The mortality rate for white women shows trends similar to those for men.  However, the white women's mortality rates did not increase as much at high BMI's as for men's. Also, white women's mortality increased more at low BMI's, but this effect is very small.

In contrast, the mortality rate of black women was barely affected by elevations in BMI!  In fact, black women's mortality was higher at low BMI's rather than high BMI's.

There were too few black men in the study to calculate the mortality rate of black men with high BMI's.  The small amount of existing data looks sort of like the data for white men.  The amount of scatter in the data from black males is to be expected because the sample group was fairly small compared to the other four groups.
 
 

The plot to the left shows the effect of BMI on the relative mortality for women.  The minimum mortality for white women is near a BMI of 23. Eyeballing the graph, relative mortality of white women exceeds 1.20 below 19 and above 29.  Notice that mortality increased dramatically for very thin women! The graph for black women shows a significant amount of scatter.  This makes it difficult to identify a meaningful minimum mortality rate.  At the extremes, a low BMI seems to result in higher mortality for black women.  High BMI's don't seem to affect black women as much. It is not clear why the elevated BMI does not appear to affect black and white women's mortality equally.  However, the effect seems to be observed in other experiments.

This graphs shows the relative mortality of white and black males. The corresponding plot for white men, is similar in shape to the plot shown for women.  The minimum mortality is between 23 and 24.  The relative mortality for white men exceeds 120% below 19 and above 28.  These are the cut-offs I picked in my discussion above. I don't even want to attempt to discuss the shape of the plot for black males.  The "jagged" shape is typical of experiment with two few participants to provide precise results.

 
 

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References

Strong Women Stay Young, Miriam E. Nelson, Ph. D.

The Exercise-Health Connection , David C. Nieman, DrPh.  1998, Human Kinetics, Champaign, Illinois.

Aerobic Fitness & Health, Roy J. Shepard, 1994 Human Kinetics, Champaign, Illinois

"Body-Mass Index and Mortality in a Prospective Cohort of U.S. Adults." 1999,  Calle, E.E., Thun, M.J., Petrelly, J.M., Rodriguez, C., Heath, C.W., New England Journal of Medicine.  Vol. 341. No. 15. pp 1097-1105.